In PowerPoint, and in other Microsoft 365 programs you typically need to sign in to a Microsoft Account so that you can access saved settings, customizations, and even some files off the cloud. You typically do this by managing your Account, right inside PowerPoint or another Microsoft 365 program such as Word and Excel. The Account tab in Backstage view allows you to sign in to your Microsoft Account, and automatically connect to your OneDrive account, and do so much more.
Learn about options within the Account tab of Backstage view in PowerPoint 365 for Windows.